1. Field of the Invention
This invention relates to a method of managing communication on an unstable error-prone channel. The invention has particular applicability to communication between transceiver nodes in high frequency (HF) radio networks.
2. Description of the Related Art
The present invention arose in the field of HF radio communications. The quality of an HF radio link is time varying. Sometimes, the quality of the link for a particular transmission frequency permits higher data rates than at other times, and sometimes transmission on that frequency is not feasible. Historically, HF radio communication has been characterized by the search for a transmission frequency which will permit acceptable link quality at a particular time, as well as uncertainty about the duration of the acceptable link.
In the last few years, there have been innovations directed to the goal of HF radio communication which is more reliable from the standpoint of an operator and which is more suitable as a link between nodes of a communication network. These innovations include protocols and methods of automatically communicating control frames, i.e., frames of control information, back and forth between HF radio nodes in a way that promotes the effective identification of suitable frequencies for transmission between the nodes and the use of new frequencies in response to changes in the link.
Even when effective methods are used to select transmission frequencies providing suitable link quality, much remains to be done in providing efficient and reliable communication over an HF link. There are problems of coordinating the communications between radio nodes, so that they enter into communication with each other in an orderly fashion and it is established which of the nodes is to transmit and which is to receive at a given time. The nodes must have a method for effectively communicating which data has been successfully transferred between them. If the methods of managing communication between the nodes can be made adaptive, efficiencies can be improved. When the nodes have a limited storage capacity, then each node must be able to control the flow of information that it receives at any time.
The present invention provides methods for addressing such issues in the particular environment of HF radio communication, which by its nature requires verification that communications have been received. The methods of the present invention are based on the conception of communicating according to certain protocols. In the framework of the ISO Network Reference Model, the hierarchial level of the protocols of the present invention is the "data link layer".